THE STERNO-CLAVICULAR ARTICULATION. 



261 



incline downward, and hence the sloping narrow shoulders and long necks so often 

 seen in feeble or in phthisical individuals. 



In very fat persons, in those suffering from organic heart disease attended with 

 dyspnoea, and in emphysematous subjects the clavicles are raised and the neck 

 thereby apparently shortened. 



THE STERNO-CLAVICULAR ARTICULATION. 



This is the only joint between the trunk and the upper extremity. The socket 

 on the upper angle of the manubrium is coated with cartilage which often extends 

 a little onto the first costal cartilage. This very shallow socket is made rather 

 more secure by the forward inclination of the manubrium and also by being rather 



Fig. 279. 



Clavicle Sterno-clavicular ligament Interclavitular ligament 



Clavicle 



First costal cartilage 



Sternum 



First costal cartilage 



Sterno-clavicular articulations from before; clavicles horizontal. 



more on the back than on the front of that bone, so that to some extent it over- 

 laps the front of the clavicle. The very irregular end of the clavicle is coated with 

 cartilage, which, however, gives it no regular nor constant shape. As a rule, it 

 is concave from before backward, but there is often a swelling at the posterior 

 lower angle. 



The interarticular fibro-cartilage ^ (Fig- 280), a disk subdividing the joint 

 into two, is the chief factor in maintaining the great security of the joint. It is a 



Fig. 280. 



Stemo 

 clavicular 

 capsule 

 opened 



Rhomboid 

 ligament 



First costal 

 cartilage 



Right sterno-clavicular joint opened. Left clavicle raised to show rhomboid ligament. Front view. 



rounded disk, thinnest in the middle and generally thickest at the upper border, 

 which is attached to the upper edge of the inner end of the clavicle, while the lower 

 border is attached to the first costal cartilage at the outer border of the joint. In 

 the main it faces upward and outward, so that the clavicle rests upon it. It is said 

 to be sometimes perforated. 



^ Discus articularis. 



